# NTSB Safety Recommendation P-77-027

**Citation:** P-77-027  
**Type / status:** guidance / guidance  
**Agency:** National Transportation Safety Board  
**Effective:** 1977-10-31  
**Published:** 1977-10-31

TAKE NECESSARY STEPS TO INSURE THAT STUDS ON COMPRESSORS COMPONENTS ARE TIGHTENED TO THE NUMBER OF FOOT-POUNDS OF TORQUE RECOMMENDED BY THE EQUIPMENT MANUFACTURER.

## Document text

NTSB safety recommendation P-77-027.

TAKE NECESSARY STEPS TO INSURE THAT STUDS ON COMPRESSORS COMPONENTS ARE TIGHTENED TO THE NUMBER OF FOOT-POUNDS OF TORQUE RECOMMENDED BY THE EQUIPMENT MANUFACTURER.

Priority: CLASS II

Overall Status: Closed - Acceptable Action

Issued Date: 1977-10-31

Adopted Date: 1977-10-13

Overall Date Closed: 1978-11-21

Synopsis: ON DECEMBER 7, 1976, A NATURAL GAS COMPRESSOR FAILED AND THEN EXPLODED AND BURNED AT AN EXXON GAS SYSTEM, INC., STATION NEAR ROBSTOWN, TEXAS. AN EMERGENCY SHUTDOWN SYSTEM WAS ACTIVATED, BUT FOUR AUTOMATED FIRE GATE VALVES DID NOT CLOSE. ANOTHER EMERGENCY CONTROL SYSTEM ALSO FAILED TO AUTOMATICALLY CLOSE THE SHUTOFF VALVES, LEADING TO TWO OF THE FIVE COMPRESSORS IN THE STATION. A SECOND EXPLOSION OCCURRED WITHIN THE BURNING BUILDING. THE FIRE KILLED ONE PERSON, INJURED TWO PERSONS, AND DESTROYED THREE ENGINE-DRIVEN COMPRESSORS AND THE COMPRESSOR BUILDING.

Ntsbnumber: DCA77MP005

Report Number: PAR-77-03

Addressee Name: ExxonMobil Corporation

Addressee Status: Closed--No Longer Applicable

Addressee Date Closed: 1978-11-21

Addressee Organization Type: P-Private Industry

Communication Date: 1977-12-20

Communication Type: Official Correspondence

Communication Contents: LTR FROM EXXON GAS SYSTEM: EXXON HAS IMPLEMENTED PROCEDURES USING CALIBRATED TORQUE WRENCHES. TORQUES ARE RECHECKED EACH TIME THEY ARE DISTURBED DURING MAINTENANCE. ALL VALVE COVER STUDS HAVE BEEN CHECKED PLUS A NUMBER OF OTHER CRITICAL BOLTS. EXXON PLANS TO COMPLETE A CHECK OF ALL CRITICAL STUDS BY MARCH 15, 1978. ULTRASONIC TESTING OF SOME BOLTS AND STUDS HAS BEEN PERFORMED BUT NOT UNDER A FORMAL SCHEDULE.

Addressee Organization Type: P-Private Industry

Communication Date: 1981-06-29

Communication Type: Official Correspondence

Communication Contents: EXXON GAS SYSTEM, INC. LTR: WE PLAN TO EXTEND THE PERIOD OF TORQUE VERIFICATION FROM 4500 OPERATING HOURS TO 9000 OPERATING HOURS BASED ON EXPERIENCED GAINED FROM 20 TORQUE VERIFICATIONS PERFORMED SINCE EARLY 1978. DATA COLLECTED TO DATE SHOWS THAT THE TORQUE VERIFICATION PERIOD CAN BE EXTENDED AND STILL MAINTAIN OUR PRESENT LEVEL OF PERSONNEL AND EQUIPMENT SAFETY.

Addressee Organization Type: P-Private Industry

Communication Date: 1979-01-05

Communication Type: Official Correspondence

Addressee Organization Type: P-Private Industry

Communication Date: 1981-08-19

Communication Type: Official Correspondence

## Provenance

- Official: Yes
- Source: <https://data.ntsb.gov/carol-main-public/sr-details/P-77-027>
- Source ID: `ntsb-pipeline`
- SHA-256: `b5d5ac39dea4bf13ad79336fa879ede08a363cc98cae9a8c77574e7c372e5110`
- Retrieved: 2026-08-20T04:57:24.741Z
- Exported: 2026-08-22T18:16:06.912Z
- Document slug: `ntsb-recommendation-p-77-027`

### Source metadata

```json
{
  "recordKind": "ntsb_safety_recommendation",
  "safetyRecommendationNumber": "P-77-027",
  "recommendationMode": "Pipeline",
  "topicMode": "Pipeline",
  "ntsbNumber": "DCA77MP005",
  "priority": "CLASS II",
  "overallStatus": "Closed - Acceptable Action",
  "overallStatusAcronym": "CAA",
  "overallDateClosed": "1978-11-21",
  "lastModifiedDate": "2016-11-15",
  "reportNumber": "PAR-77-03",
  "reportUrl": "https://www.ntsb.gov/investigations/Pages/DCA77MP005.aspx",
  "transmittalLetterUrl": "http://www.ntsb.gov/safety/safety-recs/recletters/P77_27_33.pdf",
  "addressees": [
    {
      "addresseeName": "ExxonMobil Corporation",
      "addresseeStatusAcronym": "CNLA",
      "addresseeStatus": "Closed--No Longer Applicable",
      "addresseeDateClosed": "1978-11-21",
      "addresseeDetails": [
        {
          "addresseeAcronym": null,
          "addresseeOrganizationType": "P-Private Industry",
          "isFromNtsb": false,
          "communicationDate": "1977-12-20",
          "communicationType": "Official Correspondence",
          "communicationContents": "LTR FROM EXXON GAS SYSTEM: EXXON HAS IMPLEMENTED PROCEDURES USING CALIBRATED TORQUE WRENCHES. TORQUES ARE RECHECKED EACH TIME THEY ARE DISTURBED DURING MAINTENANCE. ALL VALVE COVER STUDS HAVE BEEN CHECKED PLUS A NUMBER OF OTHER CRITICAL BOLTS. EXXON PLANS TO COMPLETE A CHECK OF ALL CRITICAL STUDS BY MARCH 15, 1978. ULTRASONIC TESTING OF SOME BOLTS AND STUDS HAS BEEN PERFORMED BUT NOT UNDER A FORMAL SCHEDULE."
        },
        {
          "addresseeAcronym": null,
          "addresseeOrganizationType": "P-Private Industry",
          "isFromNtsb": false,
          "communicationDate": "1981-06-29",
          "communicationType": "Official Correspondence",
          "communicationContents": "EXXON GAS SYSTEM, INC. LTR:  WE PLAN TO EXTEND THE PERIOD OF TORQUE VERIFICATION FROM 4500 OPERATING HOURS TO 9000 OPERATING HOURS BASED ON EXPERIENCED GAINED FROM 20 TORQUE VERIFICATIONS PERFORMED SINCE EARLY 1978.  DATA COLLECTED TO DATE SHOWS THAT THE TORQUE VERIFICATION PERIOD CAN BE EXTENDED AND STILL MAINTAIN OUR PRESENT LEVEL OF PERSONNEL AND EQUIPMENT SAFETY."
        },
        {
          "addresseeAcronym": null,
          "addresseeOrganizationType": "P-Private Industry",
          "isFromNtsb": true,
          "communicationDate": "1979-01-05",
          "communicationType": "Official Correspondence",
          "communicationContents": ""
        },
        {
          "addresseeAcronym": null,
          "addresseeOrganizationType": "P-Private Industry",
          "isFromNtsb": true,
          "communicationDate": "1981-08-19",
          "communicationType": "Official Correspondence",
          "communicationContents": ""
        }
      ]
    }
  ],
  "jurisdiction": "US"
}
```